For example, conventional contactless power-feed equipment is disclosed in JP2003-341390A.
The contactless power-feed equipment disclosed in JP2003-341390A includes a main route for traveling of a carriage and a sub route branching from the main route. The carriage is retreated to the sub route during maintenance and so on.
To feed power to the carriage traveling on the main route or the sub route, a main induction line connected to a power-supply device for outputting a high-frequency current is provided along the main route, and a sub induction line connected to the main induction line is provided along the sub route.
A first switch (first magnet contactor) for switching a connected state and a cut-off state between the power-supply device and the main induction line is provided between the power-supply device and the main induction line. The sub induction line is connected in parallel with the first switch. Moreover, a second switch (second magnet contactor) for switching a connected state and a cut-off state of the sub induction line is provided on a feed line to the sub induction line.
The effect of the configuration will be discussed below.
Typically, the first switch is in a connected state and the second switch is in a cut-off state, electrically isolating the sub induction line from the main induction line. In this state, a high-frequency current is outputted from the power-supply device to the main induction line, so that the current passes through the overall main induction line and power is fed to carriages on the main route through pickup coils. The power fed from the main induction line is received by the carriages and drives motors, allowing traveling of the carriages on the main route to transport articles.
In the case where any one of the carriages on the main route undergoes maintenance, the target carriage is temporarily retracted from the main route to the sub route before maintenance, preventing the target carriage from interfering with other carriages traveling on the main route. In this case, the power-supply device is first temporarily stopped, the first switch is placed in a cut-off state, and the second switch is placed in a connected state, thereby connecting the main induction line and the sub induction line in series. In this state, the power-supply device is operated again to output a high-frequency current to the main induction line and the sub induction line. Thus, the current passes through the main induction line and the sub induction line to feed power to the target carriage through the pickup coil. At this point, the target carriage first receives power from the main induction line and travels from the main route to the sub route. After entering the sub route, the traveling target carriage receives power from the sub induction line.
After the target carriage is fully retracted to the sub route, the power-supply device is temporarily stopped again. Thus, the first switch is placed in a connected state and the second switch is placed in a cut-off state, electrically isolating the sub induction line from the main induction line. The operation of the power-supply device is then restarted to apply a high-frequency current to the main induction line, thereby feeding power to the carriages again on the main route.
With this configuration, when power is fed to the sub induction line used for temporarily retracting the carriage, the power can be fed to the sub induction line from the same power-supply device as the main induction line without providing another power-supply device for the sub induction line. Thus, power can be inexpensively fed to the carriage on the sub route with a small space.
In the contactless power-feed equipment described in JP2003-341390A, however, a circuit impedance greatly varies, when viewed from the power-supply device, between a state in which only the main induction line is connected to the power-supply device and a state in which the main induction line is connected to the power-supply device while the sub induction line is connected to the main induction line. Thus, when power to the sub induction line is supplied or cut off during an operation of the power-supply device, the circuit impedance of the power-supply device rapidly changes, leading to fluctuations in the current of the induction line. As a result, power cannot be sufficiently supplied to the carriages instantly or for a certain time, which may cause abnormal traveling of the carriages. Thus, as has been discussed, when power to the sub induction line is supplied or cut off, the power-supply device needs to be stopped. For this reason, each time power to the sub induction line is supplied or cut off, the power-supply device is stopped or restarted, leading to a complicated switching operation.
The first switch and the second switch are connected in series with the power-supply device, allowing a current outputted from the power-supply device to directly pass through the first switch and the second switch. Hence, the first switch and the second switch need large rated currents, disadvantageously increasing the cost and space of the switches.